Movement analysis method, movement analysis apparatus, and movement analysis program

ABSTRACT

A designation unit designates a checkpoint of sporting equipment on which a swing motion is performed. A first calculation unit calculates a movement path of the sporting equipment, which is being swung, using an output of an inertial sensor. A second calculation unit calculates a posture of an interest part of the sporting equipment at the checkpoint using the output of the inertial sensor up to the checkpoint on the movement path of the sporting equipment. The display unit displays the posture of the interest part of the sporting equipment at the checkpoint.

CROSS REFERENCE

The entire disclosure of Japanese Patent Application No. 2013-217642, filed Oct. 18, 2013, is expressly incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to a movement analysis method, a movement analysis apparatus, and a movement analysis program.

2. Related Art

A movement analysis apparatus is used for analysis of a movement called a swing motion. An inertial sensor is mounted on sporting equipment or an examinee who operates the sporting equipment. The swing motion is visually reproduced based on output of the inertial sensor. As a detailed example of the movement analysis apparatus, for example, a golf swing analysis apparatus which is disclosed in JP-A-2008-73210 may be shown.

In golf, the direction of a struck ball is greatly affected by the direction of a face of a club head at an impact moment. As known, when trying to align the face of the club head by twisting the wrist immediately before the impact, the alignment is delayed and the face is not properly aligned at the impact due to twisting of the wrist, thereby negatively affecting the result of the swing. It is difficult to observe wrist behavior during a golf swing through optical motion capture using a camera or the like, and it is difficult to trace a minute wrist twisting behavior. When minute tracing is performed, it is necessary to use a plurality of high-precision cameras, thereby resulting in a large-scale measurement apparatus. In addition, measurement can be performed only indoor in optical motion capture, in which a camera or the like is used, and thus it is difficult to use the measurement apparatus in a general outdoor driving range.

An amateur golfer imposes a checkpoint for swing by himself/herself for raising a score. A back swing to the top from the address, a downswing to the impact from the top, and a follow swing reaching the finish from the impact are successively performed. Therefore, it is difficult to recognize a checkpoint during the swing. When a swing motion is visually reproduced based on the output of the inertial sensor, it is difficult to see a swing motion at a particular checkpoint of interest within the series of the swing motions. The problem is not limited to golf and is common to other sports, for example, baseball, tennis, and the like.

SUMMARY

An advantage of some aspects of the invention is to provide a movement analysis method, a movement analysis apparatus, and a movement analysis program capable of easily displaying a state of a golf club or an arm at a checkpoint visually.

(1) An aspect of the invention provides a movement analysis method including: acquiring and calculating information about movement path of sporting equipment which is being swung and information about a posture of an interest part of the sporting equipment; and outputting and displaying a state of the posture of the interest part of the sporting equipment at a designated checkpoint on the movement path of the sporting equipment.

In the movement analysis method according the aspect of the invention, the checkpoint of the sporting equipment on which a swing motion is performed is designated. For example, the movement path and the posture of the interest part of the sporting equipment are calculated using data which is output from an inertial sensor when the sporting equipment is being swung. Therefore, a position of the checkpoint on the acquired movement path of the sporting equipment may be understood. The posture of the interest part of the sporting equipment at the checkpoint, which is designated on the movement path of the sporting equipment, is displayed. When the posture is used for swing evaluation, it is possible to support the improvement of the movement of an examinee.

(2) In the movement analysis method according the aspect of the invention, the checkpoint may be designated using at least one of positional information and time information of the sporting equipment which is being swung.

Although the checkpoint is designated on the movement path of the sporting equipment, it is possible to designate the checkpoint using the positional information (for example, the same height as the eyes of the examinee or the like) or the time information (for example, time that elapses from the start of backswing or downswing or the like) of the sporting equipment. In the inertial sensor, sampling is performed per unit time and acceleration, angular velocity, and the like are detected. Detected data is managed per unit time (for example, per time or per a sampling counter number). Two-step integration is performed on the amount of change (acceleration) per unit time during, for example, a period of the sampling counter number t=1 to m, and the position of the sporting equipment in the sampling counter number t=m is acquired. The position on the movement path of the sporting equipment and time are compared with the checkpoint, with the result that a point on the movement path which coincides with or is the closest to the checkpoint is specified, and thus a sampling counter number t=m, which corresponds to the point, is specified.

(3) The movement analysis method according the aspect of the invention may further include: acquiring information about a rotation angle which varies around a long axis of a shaft section of the sporting equipment which is being swung; and associating interest part of the sporting equipment in the movement path with information about the rotation angle.

The rotation angle, which is generated around the axis of the shaft section of the sporting equipment at the checkpoint is acquired by performing integration on the angular velocity, which is acquired using the inertial sensor, within a range from an initial rotation angle position to the checkpoint. The rotation angle, which is generated around the axis of the shaft section of the sporting equipment, is an important factor which is associated with the behavior of the wrist and which indicates the direction of a hitting surface (a direction of a face surface in a case of a golf club and a direction of a string surface in a case of a tennis racket) in a case of a hitting equipment. In this manner, it is possible to recognize the behavior of the wrist at the checkpoint as the rotation angle which is generated around the axis of the shaft section of the sporting equipment at the checkpoint. When the rotation angle is used for the swing evaluation, it is possible to support the improvement of the movement of the examinee.

(4) In the movement analysis method according the aspect of the invention, the interest part of the sporting equipment may be the hitting surface. For example, in the case of the hitting equipment such as the golf club, the change during the swing in the direction of the hitting surface, such as the face surface of the club head, is the matter of concern. However, the swing is too rapid to recognize. When the posture of the hitting surface at the checkpoint is displayed, it is possible to effectively check the swing.

(5) The movement analysis method according to the aspect of the invention may further include displaying an object image which shows the interest part in association with the movement path of the sporting equipment.

In this manner, since an object which emulates the sporting equipment is displayed as a matter which shows the posture of the interest part of the sporting equipment at the checkpoint on the swing movement path, it is possible to visually evaluate the checkpoint.

(6) The movement analysis method according to the aspect of the invention may further include displaying a mark which changes direction according to a change in the state of the posture of the interest part of the sporting equipment.

When the mark is displayed, it is possible to display, for example, a wrist twisting state or the change in the angle of the hitting surface as the posture of the interest part of the sporting equipment such that the examinee easily understands the posture.

(7) The movement analysis method according to the aspect of the invention may further include displaying the state of the posture of the interest part in a direction in which an examinee gazes at the interest part of the sporting equipment. When the direction in which the examinee faces the checkpoint from the view point is set to the gaze direction, it is possible to display the posture of the interest part which is viewed from the eyes of the examinee.

(8) In the movement analysis method according the aspect of the invention, the movement path may be calculated based on output of an inertial sensor which is mounted on at least one of the sporting equipment and an examinee.

(9) In the movement analysis method according the aspect of the invention, the rotation angle may be calculated based on output of an inertial sensor which is mounted on the sporting equipment.

(10) Another aspect of the invention provides a movement analysis apparatus including: a designation unit that designates a checkpoint of sporting equipment on which a swing motion is being performed; a first calculation unit that calculates a movement path of the sporting equipment using an output of an inertial sensor; a second calculation unit that calculates a state of a posture of an interest part of the sporting equipment at the checkpoint in the movement path of the sporting equipment; and a display unit that outputs and displays the posture of the interest part of the sporting equipment at the checkpoint.

(11) Still another aspect of the invention provides a movement analysis program causing a computer to perform: acquiring information about movement path of sporting equipment, which is being swung, and information about calculation of a posture of an interest part of the sporting equipment using an output of an inertial sensor; designating a checkpoint in the movement path of the sporting equipment; and outputting and displaying a state of the posture of the interest part of the sporting equipment at the designated checkpoint.

In the movement analysis program according to the aspect, it is possible to cause the computer to perform operations of the movement analysis apparatus according to another aspect. The program may be stored in the movement analysis apparatus from the beginning, may be stored in a storage medium and then installed in the movement analysis apparatus, and may be downloaded in a communication terminal of the movement analysis apparatus from a server through a network.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a schematic diagram schematically illustrating the configuration of a golf swing analysis apparatus according to an embodiment of the invention.

FIG. 2 is a schematic diagram schematically illustrating the relationship between a movement analysis model, and a golfer and a golf club.

FIG. 3 is a block diagram schematically illustrating the configuration of an arithmetic processing circuit according to the embodiment.

FIG. 4 is a diagram illustrating an example of a checkpoint.

FIG. 5 is a diagram illustrating an output of an inertial sensor which is managed for each unit time.

FIG. 6 is a diagram illustrating a front image on which a normal view coordinate conversion is performed.

FIG. 7 is a diagram illustrating a side image on which the normal view coordinate conversion is performed.

FIG. 8 is a diagram illustrating an example of display for an image which visually expresses the movement path of a golf club and the posture of the golf club at the checkpoint.

FIG. 9 is a diagram illustrating another example of display in which view coordinates are different from those in FIG. 8.

FIG. 10 is a diagram illustrating further another example of display in which view coordinates are different from those in FIGS. 8 and 9.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. Meanwhile, the embodiment which will be described below does not inappropriately limit the content of the invention described in the appended claims, and all of the configurations, which are described in the embodiment, are not essential for the solution of the invention.

1. Configuration of Golf Club Analysis Apparatus

FIG. 1 schematically illustrates the configuration of a golf swing analysis apparatus (movement analysis apparatus) 11 according to an embodiment of the invention. The golf swing analysis apparatus 11 includes, for example, an inertial sensor 12. The inertial sensor 12 is provided with, for example, an acceleration sensor and a gyro sensor. The acceleration sensor is capable of detecting respective accelerations in triaxial directions which are perpendicular to each other. The gyro sensor is capable of individually detecting respective angular velocities around the respective axes of the three axes which are perpendicular to each other. The inertial sensor 12 outputs a detection signal. In the detection signal, an acceleration and an angular velocity are specified for each axis. The acceleration sensor and the gyro sensor relatively accurately detect information about the acceleration and the angular velocity.

The inertial sensor 12 is attached to a golf club (sporting equipment) 13. The golf club 13 includes a shaft 13 a and a grip 13 b. The grip 13 b is gripped by the hands. The grip 13 b is formed on the same axis as the shaft 13 a. The tip end of the shaft 13 a is coupled with a club head 13 c. Preferably, the inertial sensor 12 is attached to the shaft 13 a or the grip 13 b of the golf club 13. The shaft 13 a indicates a bar-shaped portion which includes the grip 13 b and reaches the club head 13 c. The inertial sensor 12 may be relatively unmovably fixed to the golf club 13. Here, in the attachment of the inertial sensor 12, one detection axis of the inertial sensor 12 is aligned on the axis of the shaft 13 a. One more detection axis of the inertial sensor 12 is aligned in a direction of the face (hitting surface) of the club head 13 c.

The golf swing analysis apparatus 11 includes an arithmetic processing circuit 14. The inertial sensor 12 is connected to the arithmetic processing circuit 14. In the connection, a predetermined interface circuit 15 is connected to the arithmetic processing circuit 14. The interface circuit 15 may be connected to the inertial sensor 12 in a wired or wireless manner. A detection signal is supplied to the arithmetic processing circuit 14 from the inertial sensor 12.

A storage device 16 is connected to the arithmetic processing circuit 14. For example, a golf swing analysis software program (movement analysis program) 17 and the relative data thereof can be stored in the storage device 16. The arithmetic processing circuit 14 executes the golf swing analysis software program 17 and implements a golf swing analysis method. A Dynamic Random Access Memory (DRAM), a high-capacity storage device unit, a nonvolatile memory, or the like can be included in the storage device 16. For example, the golf swing analysis software program 17 is temporally held in the DRAM when the golf swing analysis method is performed. The golf swing analysis software program 17 and data are held in the high capacity storage device unit such as a Hard Disk Drive (HDD). A relatively small capacity program, such as a Basic Input/Output System (BIOS), or data is stored in the nonvolatile memory.

An image processing circuit 18 is connected to the arithmetic processing circuit 14. The arithmetic processing circuit 14 transmits predetermined image data to the image processing circuit 18. A display device (display unit) 19 is connected to the image processing circuit 18. The image processing circuit 18 is provided with a view coordinate conversion unit 18A. As will be described in detail, the view coordinate conversion unit 18A performs conversion on the viewpoint and gaze direction of an image which is displayed on the display device 19. In the connection, a predetermined interface circuit (not shown in the drawing) is connected to the image processing circuit 18. The image processing circuit 18 transmits an image signal to the display device 19 in accordance with input image data. An image which is specified based on the image signal is displayed on the screen of the display device 19. A liquid crystal display or another flat panel display is used for the display device 19.

A designation unit 20 is connected to the arithmetic processing circuit 14. The designation unit 20 designates the checkpoint of the golf club 13, on which the swing motion is performed, for the arithmetic processing circuit 14. The arithmetic processing circuit 14 calculates the movement path of the interest part of the golf club 13, and calculates a rotation angle which is generated around the axis of the shaft 13 a at the checkpoint based on the output of the inertial sensor 12 up to the checkpoint on the movement path. Here, the arithmetic processing circuit 14, the storage device 16, the image processing circuit 18, and the designation unit 20 are provided as, for example, a computer apparatus.

An input device 21 is connected to the arithmetic processing circuit 14 and the designation unit 20. The input device 21 includes at least alphabet keys and numeric keys. Character information or numerical value information is input to the arithmetic processing circuit 14 from the input device 21. The input device 21 may include, for example, a keyboard. The combination of the computer apparatus and the keyboard may be replaced by, for example, a smart phone, a mobile phone terminal, a tablet Personal Computer (PC), or the like.

Here, a checkpoint which is designated by the designation unit 20 may be set based on external input data (for example, data of the height of the examinee) which is input by the input device 21. In addition, the view coordinate conversion unit 18A may be connected to the designation unit 20. If so, the view point can be set based on the data of the height of the examinee and a direction which faces the checkpoint from the viewpoint can be set to the gaze direction.

2. Movement Analysis Model

The arithmetic processing circuit 14 defines a virtual space. The virtual space is formed in a 3-dimensional space. The 3-dimensional space specifies an actual space. As shown in FIG. 2, the 3-dimensional space includes an absolute reference coordinate system (world coordinate system) Σxyz. In the 3-dimensional space, a 3-dimensional movement analysis model 26 is constructed along the absolute reference coordinate system Σxyz. A bar 27 of the 3-dimensional movement analysis model 26 is point restrained by a fulcrum 28 (coordinate x). The bar 27 3-dimensionally operates as a pendulum around the fulcrum 28. It is possible to move the position of the fulcrum 28. Here, the position of the tip end of the club head 13 c is specified by a coordinate xh along the absolute reference coordinate system Σxyz.

The 3-dimensional movement analysis model 26 corresponds to a model of the golf club 13 when a swing is performed. The shaft 13 a of the golf club 13 is projected as the bar 27 of the pendulum. The grip 13 b is projected as the fulcrum 28 of the bar 27. The inertial sensor 12 is fixed to the shaft 13 a. The inertial sensor 12 outputs an acceleration signal and an angular velocity signal. In the acceleration signal, an acceleration signal which includes a gravity acceleration g is output.

Similarly, the arithmetic processing circuit 14 fixes a local coordinate system (sensor coordinate system) Σs to the inertial sensor 12. The origin of the local coordinate system Σs is set to the origin of the detection axis of the inertial sensor 12. The Y axis of the local coordinate system Σs coincides with the long axis of the shaft 13 a as shown in FIG. 1. The x axis of the local coordinate system Σs coincides with a struck ball direction which is specified as a direction of a face as shown in FIG. 1. Therefore, based on the local coordinate system Σs, a fulcrum position l_(sj) is specified as (0, l_(sjy), 0) as shown in FIG. 2. Similarly, the position l_(sh) of the club head 13 c is specified as (0, l_(shy), 0).

3. Swing Trace Calculation

FIG. 3 schematically illustrates the configuration of the arithmetic processing circuit 14 according to the embodiment. The arithmetic processing circuit 14 includes a swing trace calculation unit 31 as a first calculation unit and a rotation angle calculation unit 32 as a second calculation unit. The swing trace calculation unit 31 is connected to the inertial sensor 12. An output signal is supplied to the swing trace calculation unit 31 from the inertial sensor 12. Here, the output of the inertial sensor 12 includes accelerations which are respectively detected along the perpendicular three axes, and angular velocities which are respectively detected around the perpendicular three axes. The swing trace calculation unit 31 detects the position and the posture of the golf club 13 based on the output of the inertial sensor 12. The swing trace calculation unit 31 detects, for example, the positions of the grip 13 b and the club head 13 c which are moving. In the detection, the swing trace calculation unit 31 calculates the acceleration of the grip 13 b according to, for example, subsequent Expression (1). In the calculation of the acceleration, the swing trace calculation unit 31 specifies the position l_(sj) of the grip 13 b according to the unique local coordinate system Σs of the inertial sensor 12. In the specification, the swing trace calculation unit 31 acquires positional information from the storage device 16. The position l_(sj) of the grip 13 b is stored in the storage device in advance. The position l_(sj) of the grip 13 b may be designated through, for example, the input device 21. In Expression (1), α_(sj) indicates the acceleration of the grip, as indicates the acceleration which is measured by the inertial sensor 12, and ωs indicates the angular velocity which is measured by the inertial sensor 12.

α_(sj)=α_(s)+{dot over (ω)}_(s) ×l _(sj)+ω_(s)×(ω_(s) ×l _(sj))+g  (1)

The swing trace calculation unit 31 calculates the moving velocity of the grip 13 b based on the calculated acceleration. Here, an integration process is performed on the acceleration with a prescribed sampling interval dt according to subsequent Expression (2). N indicates the number of samples (hereinafter, the same).

$\begin{matrix} {{{V_{sj}(0)} = 0}{{V_{sj}(t)} = {\sum\limits_{n = 1}^{t}{{{\alpha_{sj}(n)} \cdot {t}}\mspace{14mu} \left( {{t - 1},\ldots \;,N} \right)}}}} & (2) \end{matrix}$

Further, the swing trace calculation unit 31 calculates the position of the grip 13 b based on the calculated velocity. Here, the integration process is performed on the velocity with the prescribed sampling interval dt according to subsequent Expression (3).

$\begin{matrix} {{P_{sj}(t)} = {\sum\limits_{n = 1}^{t}{{{V_{sj}(n)} \cdot {t}}\mspace{14mu} \left( {{t = 1},\ldots \;,N} \right)}}} & (3) \end{matrix}$

The swing trace calculation unit 31 specifies the position of the local coordinate system Σs (or the position of the grip 13 b) in a virtual 3-dimensional space in advance. When the displacement of the local coordinate system Σs or the displacement of the grip 13 b is converted into a coordinate system in the virtual 3-dimensional space, the position of the golf club 13 is specified.

Similarly, the swing trace calculation unit 31 detects the position of the club head 13 c according to subsequent Expressions (4) to (6). In the detection of the position, the swing trace calculation unit 31 specifies the position l_(sh) of the club head 13 c according to the unique local coordinate system Σs of the inertial sensor 12. In the specification, the swing trace calculation unit 31 acquires the positional information from the storage device 16. The position l_(sh) of the club head 13 c is stored in the storage device 16 in advance. The position l_(sh) of the club head 13 c may be designated through, for example, the input device 21.

$\begin{matrix} {{\alpha_{sh} = {a_{s} + {\omega_{s} \times _{sh}} + {\omega_{s} \times \left( {\omega_{s} \times _{sh}} \right)} + g}}{{V_{sh}(0)} = 0}} & (4) \\ {{V_{sh}(t)} = {\sum\limits_{n = 1}^{t}{{{\alpha_{sh}(n)} \cdot {t}}\mspace{14mu} \left( {{t = 1},\ldots \;,N} \right)}}} & (5) \\ {{P_{sh}(t)} = {\sum\limits_{n = 1}^{t}{{{V_{sh}(n)} \cdot {t}}\mspace{14mu} \left( {{t = 1},\ldots \;,N} \right)}}} & (6) \end{matrix}$

The swing trace calculation unit 31 specifies the position l_(sh) of the club head 13 c according to the unique local coordinate system Σs of the inertial sensor 12 as described above, and then converts the position l_(sh) of the club head 13 c into the coordinate system in the virtual 3-dimensional space. That is, the position P_(sh)(t) of the club head 13 c is shown by coordinates (x, y, z) in the virtual 3-dimensional space shown in FIG. 1.

4. Calculation of Rotation Angle Around Axis of Shaft

The rotation angle calculation unit 32 is connected to the inertial sensor 12 and the designation unit 20. An output from the inertial sensor 12 is supplied to the rotation angle calculation unit 32. The rotation angle calculation unit 32 detects the rotation angle θ_(m) (m=1, . . . , N) of the grip 13 b around the axis from the initial position of an angular position “0°” to the checkpoint based on the output of the inertial sensor 12. In the detection, the rotation angle calculation unit 32 integrates the amount of change in the rotation angle per unit time (angular velocity ω_(n)) as shown in subsequent Expression (7).

$\begin{matrix} {{\theta_{0} = 0}{\theta_{m} = {\sum\limits_{n = 1}^{m}{{\omega_{n} \cdot {t}}\mspace{14mu} \left( {1 \leq m < N} \right)}}}} & (17) \end{matrix}$

An integration period in Expression (7) ranges from the initial position n=1 to the checkpoint n=m, and integration is performed on the angular velocity ω_(n) which is output from the inertial sensor (here, a gyro sensor) 12 during the period. In this manner, the rotation angle θ_(n), is calculated at the checkpoint of the grip 13 b.

In the detection of the rotation angle θ_(m), at the checkpoint, the rotation angle calculation unit 32 detects the initial position of the grip 13 b around the axis of the grip 13 b (the same axis of the shaft 13 a) based on the output of the inertial sensor 12. In the detection, the rotation angle calculation unit 32 acquires the angular velocity at address around a first detection axis (here, around the y axis) which is parallel to the shaft 13 a by the inertial sensor 12. The rotation angle calculation unit 32 sets the acquired angular velocity to an initial value. The angular velocity is not generated around the y axis at address. Therefore, when the grip 13 b stops at an angular velocity of “0 (zero)”, the angular position is set to “0° (zero degree)” (=initial position).

The angular velocity ω_(n) is sequentially input to the rotation angle calculation unit 32 from the inertial sensor (gyro sensor) 12. Therefore, a checkpoint is designated to the rotation angle calculation unit 32. If the end of the integration period is acquired, the rotation angle calculation unit 32 can calculate the rotation angle θ_(m) of the grip 13 b at the checkpoint.

5. Designation of Checkpoint

Although the checkpoint can be designated as positional information or time information in the movement path of the golf club 13, a case in which designation is performed using the positional information will be described below.

FIG. 4 is a diagram illustrating an example of the checkpoint. In the golf driving range, there is a case in which the golf club 13 is stopped during downswing facing the impact from the top, and the direction of the face of the club head 13 c at that time is recognized as a checkpoint. In the example, the club head 13 c is stopped at, for example, the height of the eyes of a golfer. The checkpoint is a height H1 up to the club head 13 c. The checkpoint (height) H1 can be designated in such a way that the golf swing analysis apparatus 11 acquires a height H2 of the golfer. In the embodiment, height data H2 of an examinee is input by the input device 21. The designation unit 20 can designate the checkpoint (height) H1 by performing an operation of H1=H2×α using, for example, a coefficient α (α<1) It is possible to set the coefficient α to, for example, α=0.8 as the coefficient of the height of eyes of the examinee, who is a little bent.

FIG. 5 illustrates an example of data which is detected by the inertial sensor 12. For example, a sampling counter number t (t=1 to N) is attached to a top bit of the data of the acceleration and the angular velocity of three axes, which are transmitted from the inertial sensor 12, as shown in FIG. 5. Meanwhile, the data may be stored in the storage device 16 or a storage unit inside the arithmetic processing circuit 14. The sampling counter number t coincides with a symbol t in Expression (7) which is used when the swing trace calculation unit 31 calculates the position P_(sh)(t) of the club head 13 c. That is, the position P_(sh)(t) of the club head 13 c, which is calculated by the swing trace calculation unit 31 based on Expression (7), is calculated per the sampling counter number t.

The position P_(sh)(t) of the club head 13 c, which is calculated per the sampling counter number t, is input to the designation unit 20 from the swing trace calculation unit 31. The designation unit 20 determines whether or not the height (z coordinate) of the position P_(sh)(t) of the club head 13 c coincides with the checkpoint (height) H1, or acquires the sampling counter number t=m which is the closest value.

In this manner, the designation unit 20 designates the sampling counter number t=m, which corresponds to the checkpoint (height) H1, for the rotation angle calculation unit 32. Based on Expression (7), the rotation angle calculation unit 32 calculates the rotation angle θ_(m) which is generated around the axis of the shaft 13 a at the checkpoint H1 on the movement path of the club head 13 c based on the output (t=1 to m) of the inertial sensor 12 up to the checkpoint H1.

6. Display

The arithmetic processing circuit 14 includes an image data generation unit 34. The image data generation unit 34 is connected to the swing trace calculation unit 31 and the rotation angle calculation unit 32. An output signal is supplied to the image data generation unit 34 from the swing trace calculation unit 31 and the rotation angle calculation unit 32. The image data generation unit 34 includes a movement trace image generation unit 35, a surface rotation image generation unit 36, and a cube image generation unit 37. The movement trace image generation unit 35 generates images (R1 and R2 shown in FIGS. 8 to 10 which will be described later) to visually display the movement path of the golf club 13 based on the position and the posture of the golf club 13. The surface rotation image generation unit 36 generates an object image (image 41 shown in FIGS. 8 to 10) for displaying a face which is prescribed on the golf club 13 and rotates around the axis of the shaft 13 a. The cube image generation unit 37 generates an image of a cube (a mark 42 shown in FIGS. 8 and 9) which has a ridgeline parallel to the axis of the grip 13 b. In the cube, one plane, which extends parallel to the axis of the grip 13 b and has a geometric-shaped outline (here, a quadrate outline), is prescribed. The object image 41 of the face surface and the plane 43 of the cube 42 change directions around the axis of the grip 13 b according to the rotation angle θ_(m) of the grip 13 b when the club head 13 c is at the checkpoint. Images, acquired when the club head 13 c is at the checkpoint, are associated with each other, and output from the image data generation unit 34 as a single piece of image data. Meanwhile, the mark can have a three-dimensional shape, such as a curved surface or a sphere other than a cube, in addition to the plane or cube.

The arithmetic processing circuit 14 includes a drawing unit 38. The drawing unit 38 is connected to the image data generation unit 34. Image data is supplied to the drawing unit 38 from the image data generation unit 34. The drawing unit 38 draws an image which visually displays the movement path of the golf club 13 based on the output signal of the movement trace image generation unit 35, and displays the image on the display device 19. The drawing unit 38 overlaps the face image (object) 41 and the cube image (mark) 42 on the image of the movement path of the golf club 13 for each position. As a result, in the virtual 3-dimensional space, an image which is acquired by associating the movement path of the golf club 13 with the rotation angle of the face and the rotation angle of the cube at the checkpoint and which is visually displayed, is generated.

7. Operation of Golf Swing Analysis Apparatus

An operation of the golf swing analysis apparatus 11 will be simply described. First, a golf swing of a golfer is measured. Prior to the measurement, necessary information is input to the arithmetic processing circuit 14 from the input device 21. Here, according to the 3-dimensional movement analysis model 26, the position l_(sj) of the fulcrum 28 according to the local coordinate system Σs and the rotation matrix R0 of an initial posture of the inertial sensor 12 are prompted to be input. In addition, data of the height of the golfer is input to the designation unit 20 from the input device 21. The input information is managed, for example, under a specific identifier. The identifier may identify a specific golfer.

Prior to the measurement, the inertial sensor 12 is attached to the shaft 13 a of the golf club 13. The inertial sensor 12 is fixed to the golf club 13 such that relative displacement is not possible. Here, one detection axis of the inertial sensor 12 is aligned on the axis of the shaft 13 a. One detection axis of the inertial sensor 12 is aligned in a struck ball direction which is specified as the direction of the face (hitting surface).

Prior to the execution of golf swing, measurement performed by the inertial sensor 12 starts. When a motion starts, the inertial sensor 12 is set to a predetermined position and posture. The position and the posture are specified in a rotation matrix R0 of the initial posture. The inertial sensor 12 continuously measures the acceleration and the angular velocity at a specific sampling interval. The sampling interval prescribes a measurement resolution. The detection signal of the inertial sensor 12 is transmitted to the arithmetic processing circuit 14 in real time. The arithmetic processing circuit 14 receives a signal which specifies the output of the inertial sensor 12.

The golf swing starts from address and reaches the follow-through and the finish through take back, half way back, top to downswing, and impact. If the golf club 13 is swung, the posture of the golf club 13 changes according to a time axis. The inertial sensor 12 outputs the detection signal according to the posture of the golf club 13. At this time, the swing trace calculation unit 31 detects the position of the golf club 13, in particular, the club head 13 c based on the output of the inertial sensor 12. The designation unit 20, to which the position of the club head 13 c is input from the swing trace calculation unit 31, compares the position and the checkpoint. The designation unit 20 acquires the sampling counter number t=m when the swing trace calculation unit 31 calculates the position corresponding to the checkpoint, and instructs the rotation angle calculation unit 32. The rotation angle calculation unit 32 calculates the angular position of the grip 13 b around the axis of the grip 13 b at the checkpoint according to Expression (7) based on the output of the inertial sensor 12 up to the checkpoint H1 on the movement path of the club head 13 c. The image data generation unit 34 generates 3-dimensional image data (for example, polygon data) which specifies an image of the face and an image of the cube at the checkpoint in association with the movement path of the golf club 13. The drawing unit 38 draws the image of the face 41 and the image of the cube 42 in association with the movement path T of the golf club 13 based on the 3-dimensional image data.

The drawing data is transmitted to the image processing circuit 18, and an image is displayed on the screen of the display device 19 according to the drawing data. The image processing circuit 18 includes a view coordinate conversion unit 18A. The view coordinate conversion unit 18A has a well-known function to perform view coordinate conversion such that an image, viewed from the view point toward the gaze direction, is displayed on the display device 19. For example, the view point is set on the z axis by the absolute reference coordinate system (x, y, z) shown in FIG. 1, and a front image, which is acquired by performing normal view coordinate conversion such that the gaze direction from the view point is set to the z direction, is shown in FIG. 6. Similarly, the view point is set on the x axis, a side image, which is acquired by performing the normal view coordinate conversion such that the gaze direction from the viewpoint is set to the x direction, is shown in FIG. 7. Meanwhile, in FIGS. 6 and 7, a backswing movement path is R1, and a downswing movement path is R2.

In the embodiment, the front image or the side image shown in FIGS. 6 and 7 may be used. FIG. 8 illustrates the posture of the face of the club head 13 c at the checkpoint, which is displayed in, for example, the front image which is the same as in FIG. 6. Furthermore, for example, view coordinate conversion, in which the vicinity of the eyes of a golfer is set to a view point 1 and which includes a gaze direction 1 toward the checkpoint from the view point 1 in FIG. 7, can be illustrated in FIG. 9. The gaze direction 1 is the same as the gaze direction S from the view point P shown in FIG. 4. That is, in FIG. 9, the posture of the face of the club head 13 c at the checkpoint viewed from the eyes of the golfer is displayed by the movement analysis apparatus 11, similarly to FIG. 4 when the golf club 13 is swung at the checkpoint without stopping. According to the display example in FIG. 9, it is excellent in that the checkpoint acquired when exercise, which is used as in FIG. 4, is performed (when the golf club is stopped) can be compared with the checkpoint when the golf club is swung without stopping. As further another example, in FIG. 7, view coordinate conversion, in which a view point 2 is set obliquely above and behind the golfer and which includes a gaze direction 2 toward the golfer from the view point 2 in FIG. 7, can be illustrated in FIG. 10.

FIGS. 8 to 10 illustrate the backswing movement path R1 and the downswing movement path R2. In addition, FIGS. 8 to 10 illustrate an object 41 which indicates the face of the club head 13 c which rotates around the axis of the shaft 13 a. In addition, FIGS. 8 and 9 illustrate a cube 42 which is a mark. Since the shaft 13 a of the sporting equipment 13 has a bar shape, it is difficult for the examinee to grasp the amount of rotation even though the rotation around the axis of the shaft 13 a is displayed as the object 41. Therefore, when the mark 42 (FIGS. 8 and 9) which indicates the change in rotation angle generated around the axis of the shaft 13 a of the sporting equipment 13 is displayed in conjunction with the movement path of the sporting equipment 13, it is possible to display the wrist twisting state and the change in the angle of the struck ball surface for easy understanding by the examinee.

The plane 43 of the cube 42 in the image changes the direction according to the rotation of the grip 13 b and the shaft 13 a. The rotation of the grip 13 b, that is, the rotation of the wrist is expressed through the rotation of the plane 43. In this manner, the examinee can clearly grasp the rotation of the wrist at the checkpoint based on the image. The examinee can improve a swing posture according to such a grasp. In particular, the cube 42 reflects the perpendicular three axes of the grip 13 b. As a result, the examinee can ideally recognize the behavior of the wrist at the checkpoint clearly.

In the representation of the swing motion, the face 41 at the checkpoint is specified in the image. In this manner, the rotation of the wrist at the checkpoint with the golf club 13 itself is represented. The examinee can visually recognize the behavior of the golf club 13. The examinee can improve the swing posture through the recognition. Meanwhile, the first image and the second image may be displayed in parallel or overlapping on the display device 19. In this manner, it is possible to compare different swings of the same golfer. Further, it is possible to compare the swing of a person with the swing of an advanced learner.

Meanwhile, in the above embodiment, the individual functional block of the arithmetic processing circuit 14 is realized by executing the golf swing analysis software program 17. However, the individual functional block may be realized by hardware without resorting to software processing. In addition, the golf swing analysis apparatus 11 may be applied for analysis of swing of sporting equipment (for example, a tennis racket, a table tennis racket, or a baseball bat) which is gripped and swung by hand. In addition, although the swing trace calculation unit 31 and the rotation angle calculation unit 32 in FIG. 3 are separately described, the swing trace calculation unit 31 and the rotation angle calculation unit 32 may collectively function as a single calculation unit.

Although the embodiment has been described in detail as above, those skilled in the art can easily understand that various modifications are possible without substantially departing from the novelty and advantages of the invention. Therefore, all of such modification examples are included in the scope of the invention. For example, in the specification or drawings, a term, which is described at least once with a different term having wider or synonymous meaning, can be replaced with the different term at any place of the specification or the drawings. In addition, the configurations and operations of the inertial sensor 12, the golf club 13, the arithmetic processing circuit 14, the designation unit 20, the 3-dimensional movement analysis model 26, the swing trace calculation unit 31, the rotation angle calculation unit 32, and the like are not limited to the description of the embodiment, and various modifications are possible. For example, the arithmetic processing circuit 14, the image processing circuit 18, the swing trace calculation unit 31, and the rotation angle calculation unit 32 may be embodied by a single processing unit, such as a central processing unit (CPU), more than one processing unit, or may be embodied by one or more special purpose circuits. The processing units are not limited to CPUs, and may be provided by any other type of processing unit. In addition, it is possible to apply the invention to sports, such as tennis or baseball, in which a swing motion is used, in addition to golf. 

What is claimed is:
 1. A movement analysis method comprising: acquiring information about a swing movement path of sporting equipment and information about a posture of an interest part of the sporting equipment; and outputting a state of the posture of the interest part of the sporting equipment at a designated checkpoint in the swing movement path of the sporting equipment.
 2. The movement analysis method according to claim 1, wherein the designated checkpoint is designated using at least one of positional information and time information of the sporting equipment which is being swung.
 3. The movement analysis method according to claim 1, further comprising: acquiring information about a rotation angle of the sporting equipment, the rotation angle varying around a long axis of a shaft section of the sporting equipment during a swing; and associating the interest part of the sporting equipment in the swing movement path with the information about the rotation angle.
 4. The movement analysis method according to claim 1, wherein the interest part of the sporting equipment is an impact surface.
 5. The movement analysis method according to claim 1, further comprising: displaying an object image which shows the interest part in association with the swing movement path of the sporting equipment.
 6. The movement analysis method according to claim 5, further comprising: displaying a mark which changes an orientation according to change in the state of the posture of the interest part of the sporting equipment.
 7. The movement analysis method according to claim 1, further comprising: displaying the state of the posture of the interest part in a viewing position, the viewing position being a position at which an examinee looks at the interest part of the sporting equipment during a swing.
 8. The movement analysis method according to claim 1, wherein the swing movement path is calculated based on output of an inertial sensor which is mounted on at least one of the sporting equipment and an examinee.
 9. The movement analysis method according to claim 3, wherein the rotation angle is calculated based on an output of an inertial sensor which is mounted on the shaft section of the sporting equipment.
 10. A movement analysis apparatus comprising: a designating section that designates a checkpoint of sporting equipment which is being swung; a path calculating section that calculates a movement path of the sporting equipment using an output of an inertial sensor; a posture calculating section that calculates a state of a posture of an interest part of the sporting equipment at the checkpoint in the movement path of the sporting equipment; and an output section that outputs the posture of the interest part of the sporting equipment at the checkpoint.
 11. A non-transitory computer-readable medium storing a movement analysis program, the program causing a computer to execute the steps of: acquiring information about movement path of sporting equipment, which is being swung, and information about a posture of an interest part of the sporting equipment using an output of an inertial sensor; designating a designated checkpoint in the movement path of the sporting equipment; and outputting a state of the posture of the interest part of the sporting equipment at the designated checkpoint.
 12. The movement analysis method according to claim 1, the method further comprising: acquiring information about a predetermined condition regarding at least one of information of an examinee and a dimension of the sporting equipment which is being swung.
 13. The movement analysis method according to claim 12, wherein the designated checkpoint is designated based on the predetermined condition.
 14. A movement analysis apparatus comprising: a storage section that stores a predetermined condition regarding at least one of information of an examinee and a dimension of sporting equipment which is being swung; a designating section that designates a checkpoint of sporting equipment during a swing based on the predetermined condition; a path calculating section that calculates a movement path of the sporting equipment using an output of an inertial sensor; a posture calculating section that calculates a state of a posture of an interest part of the sporting equipment at the checkpoint in the movement path of the sporting equipment; and an output section that outputs the posture of the interest part of the sporting equipment at the checkpoint.
 15. The movement analysis apparatus according to claim 14, wherein the predetermined condition is information about a height of the examinee.
 16. The movement analysis apparatus according to claim 14, wherein the predetermined condition is a length of the interest part from the inertial sensor.
 17. The movement analysis apparatus according to claim 14, wherein the output section outputs the movement path of the sporting equipment, the movement analysis apparatus further comprising: a display device configured to display the posture of the interest part of the sporting equipment at the checkpoint in association with the movement path. 